1. Field of the Invention
This invention relates generally to a document transmission module connectable to conventional source of digitized image data such as a computer, scanner, phone line, telefacsimile machines and the like. In one embodiment, the invention may be implemented using a document transmission module connected between a conventional telefacsimile source (also referred to as a host telefacsimile unit) and a communication interface. The document transmission module has the ability to distinguish recognizable characters from unknown graphics, and to transmit codes for the recognizable characters with less data than that required by bit maps or employed in conventional telefacsimile devices.
2. Related Art
Conventional telefacsimile or fax machines scan a document to produce pixel data. This pixel data is then compressed and sent over communications media such as telephone lines to a receiving fax machine. A problem with such telefacsimile machines is the absence of maximal data compression for characters due to the lack of efficient coding for character data.
U.S. Pat. No. 4,410,916 issued to Pratt discloses a dual mode telefacsimile compression technique, wherein spatially isolated black and white pixel patterns expected to recur in a document are extracted and coded by a matching process. A trial block area around a block pixel is examined to isolate symbols. Isolated symbols are labeled and a set of measured features is used to build a library. Each symbol subsequently found in trial blocks of the scan is compared to the features of the blocks to eliminate unworthy symbols from a template matching process. If the matching error falls below a threshold, the identification of the matching library number is stored for later coding. If no symbol is found within a trial block, the block is encoded as residue using a modified relative address code and processed separately. The symbols""s library identification codes and residue codes and the codes of unsuccessfully compared symbols are transmitted to receivers. The specialized coding in Pratt is quite slow due to the need to perform extensive template matching for each character. Pratt does not distinguish text from graphics, and fails to provide flexible operation in other modes, such as transmission of bit maps, so that communication is only possible among similarly equipped units.
U.S. Pat. No. 4,566,127 to Sekiya discloses a telefacsimile having an optical character reader and a central processing unit which provide coding character information and a telefacsimile mode. However, Sekiya is limited to operation with documents of a predetermined format in which character groups having predetermined attributes are disposed in a first location of the document and images having predetermined attributes are disposed in a predetermined second location.
U.S. Pat. No. 4,922,545 to Endo discloses a telefacsimile image coding method in which an input image pattern which occurs once is sequentially scanned and conventionally encoded. Patterns appearing twice or more, according to a matching pattern, are encoded by position coordinates and a library identification code is added at the time the pattern is registered in a library. This system is primarily a handwriting recognition system, and there is no provision for flexible operation with units not similarly equipped.
An objective of this invention is to provide a document transmission module, connectable to any one of millions of conventional sources of data such as computer outputs, scanners, phone lines, telefacsimile machines or the like which provides quicker transmission of documents and a higher quality printout than conventional mechanisms.
In one embodiment of the invention there is provided a document transmission protocol module, connectable to conventional telefacsimile machines or sources, which permits transmission of documents in either a high speed mode or a standard mode.
A still further object of the invention is to provide a document transmission module, connectable, for example, to conventional telefacsimile devices which, while providing the above advantages when communicating with other suitably equipped telefacsimile devices, is still capable of communicating with conventional telefacsimile machines.
A document transmission module, according to this invention, has the capability of recognizing characters on a document. Characters are converted by an optical character recognition (OCR) means to produce character codes for recognizable ASCII or the like. Any unrecognizable characters and areas of the document which are graphics or other non-character information are coded according to a recognized image data transmission protocol. The coding of both character and non-character information includes means for enabling data from both coding modes to be reproduced in its original spatial relationship at a destination device (computer, facsimile machine, printer, display monitor etc). The document is transmitted as a combination of character codes, such as ASCII codes, and other recognized data transmission protocols i.e., telefacsimile codes or other generally available image data transmission formats. This results in higher compression ratios for documents containing a number of recognizable characters and therefore allows reducing the transmission time of a document.
The document transmission module according to the invention may operate in either a standard mode or in the described high speed mode. The document transmission module receives input from a conventional data source to which it is connected and is capable of expanding conventionally compressed data (i.e., fax data) to a format compatible with its OCR engine, if such engine cannot process the compressed data. The module would typically query or otherwise determine whether a receiving machine (or a conventional device equipped with a similar document transmission module) can process the high speed mode containing character code data and non-code data or whether the receiving machine can only process standard non-code data (i.e., telefacsimile data). The transmitting module may automatically switch modes between the described high speed mode or the standard mode according to whether the receiving machine can process the high speed mode. Therefore, a document transmission module according to this invention is capable of communicating with existing data sources such as telefacsimile devices, computer outputs, scanner outputs and the like.
In the high speed mode, since character codes, in ASCII or other defined character sets, are sent and then received by the receiving device, characters may be printed as fully formed characters rather than as low resolution pixel data. Therefore, documents sent using this document transmission module can be more legible in the character areas than documents sent by conventional non-coded (pixel by pixel) devices (i.e., facsimile machines).